Memories are made with sleep

Sleep can rescue memories that are starting to fade.

If you're studying for a test, rehearsing for a play, or memorizing a difficult piece of music, the best thing you can do for your memory is to get to bed on time. Two new studies suggest that we form memories in several stages, and sleep may be the most important part of all.

Sleep can help restore memories.

In the first study, 84 college students learned to identify a series of similar-sounding words produced by a machine. Right after the training, participants performed well on a word recall test. Later in the day, they didn't do as well. After a good night's sleep, however, their performance rebounded to where it had been the morning before.

For the second study, a different group of researchers taught 100 adults to press a specific sequence of five number keys on a keyboard. The adults had to do it again and again as accurately and quickly as possible. Six hours later, they remembered the original sequence even when they had just learned a second sequence. A night's sleep helped them do still better.

Memory formation may require more than just one night of good sleep, the researchers found. On the second day, if participants were tested on the first sequence and then immediately learned a second sequence, their memory for the first faded badly by day 3. If they weren't retested on the first before learning a second sequence, the adults remembered both sequences the following day.

These results suggest that briefly recalling something a day after you learned it can actually get in the way of future recall, especially if you're learning something new right after. Lasting memories don't seem to form all at once. Instead, you need sleep to help reinforce memories and keep them from fading away.

So, if you really want to remember something, study until bedtime. But don't stay up all night. You may learn less, but you'll remember a whole lot more.—E. Sohn